1. Field of the Invention
This invention relates to switches for routing the path an electronic signal travels, and more particularly to blocking switch matrices for routing the path an electronic signal travels from an input transmission line to one of a series of output transmission lines within an electronic circuit assembly.
2. Description of the Prior Art
Blocking switch matrices are well known in the electronics industry. Present blocking switch matrices are constructed in accordance with two approaches. The first utilizes orthogonal three-dimensional arrangements of transmission lines, directional couplers and solid state switches that are fabricated and assembled using Hybrid Microwave Integrated Circuitry (HMIC) techniques. The second utilizes Monolithic Microwave Integrated Circuitry (MMIC) techniques wherein crossed, nonintersecting transmission lines, interconnections and switch elements are integrated on a multilevel substrate (chip) using semiconductor processing techniques.
Switching devices fabricated utilizing the MMIC technique are preferable over switches made in accordance with the HMIC technique because the MMIC switches are smaller in size and, due to fewer welded interconnections, have improved reliability. However, both the HMIC and MMIC techniques suffer from drawbacks. Specifically, the HMIC technique produces assemblies which are both bulky and unreliable because of numerous welded interconnections. In addition, the switch matrices produced by the HMIC technique are relatively costly to produce due to the significant amount of manual labor required for assembly. The MMIC technique is impractical because chip size becomes very large due to the inherent circuit complexity, even for low order switching matrices, causing wafer yield to be low and therefore wafer cost to be high. Finally, both techniques require the splicing of input and output transmission lines for the insertion of either the HMIC or MMIC switching devices which can increase the time and cost required to produce such devices.